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Part of: Clear language

Simple sentences

Last updated: 16 September, 2022

Following this helps people with:

  • time pressures: simply written content is easier to scan and absorb

  • stress: when anxious it's harder to comprehend things

  • multi-tasking: it's harder to comprehend convoluted content

  • cognitive impairments: simple sentences carry less cognitive load

  • visual impairments: clear, concise copy is shorter to read

  • motor impairments: clear, concise content needs less navigation


Short, simple sentences are better on the web than long, protracted prose with complex syntax. 

WCAG says: "using the clearest and simplest language appropriate is highly desirable." 

1. Make your average sentence 15 words long.

2. Avoid complex sentence structures.

Usability evidence

1. Make your average sentence 15 words long.

The maximum sentence length for a good level of comprehension is 25 words. Split long sentences up into 2 or 3, or use bullet points.

Oxford Guide to plain English, GOV.UK and linguists agree:

  • 15 word sentences are more likely to be comprehensible

  • 25 words is a good maximum sentence length limit

  • above 40 words sentences are hard to comprehend easily


"This sentence is about 15 words long and is easy to understand."

A mix of slightly shorter and slightly longer sentences can make reading more interesting.

2. Avoid complex sentence structures.

They are less easy to comprehend quickly. Understanding them requires more cognitive effort than simple sentences.

Complexity depends on:

  • number of clauses in a sentence, the more clauses the more complex it is

  • distribution of associated words across the sentence – how easily can the brain 'parse a phrase': recognise, connect and comprehend words that together convey meaning


"The red fox jumped over the gate." – easier to understand 
"The fox, which was red, over the gate jumped." – harder to understand

Usability evidence

Oxford Guide to plain English , Oxford University Press, 2013

Writing for GOV.UK, UK Government website

'Sentence length: why 25 words is our limit', Inside GOV.UK, UK Government blog, 2014

'Content design', Sarah Richards, 2017

'Short sentences boost readability. Nearly 140 years of research proves it' A. Wylie, a collection of studies since 1880s, 2018

'Indlish: The book for every English-speaking Indian', J. Sanyal, 2006. Book.

'The role of word difficulty and sentence length in text comprehension', T. M. Duffy and P. K. U'Ren, 1982

'Guidelines for Document Designers', Redish, J.,1981, new 2014 introduction. Online PDF.

'The Influence of Semantics and Syntax on What Readers Remember', C. S. Isakson and J. H. Spyridakis, 1999

'How the brain attunes to sentence processing: Relating behavior, structure, and function', A. Fengler, L. Meyer, A. D. Friederici, National Center for Biotechnology Information

'Functional Analysis of Clause Complex in the Language of News Websites Texts: A Comparative Study of Two Articles', F. M. S. Eid, International Journal of Scientific and Research Publications, Volume 6, Issue 6, June 2016

Reading Level, Understanding SC 3.1.5, WCAG, 2008

'Readability Assessment of Internet-Based Consumer Health Information', T. M. Walsh and T. A. Volsko in Respiratory Care October 2008, 53 (10) 1310-1315

'The research basis of plain language techniques: Implications for establishing standards', K. Schriver, PhD, Dr. A. L. Cheek, M. Mercer, Center for Plain Language, November 20, 2008, Mexico City

'Readability Levels of Health-Based Websites: From Content to Comprehension', M. Schutten, A. McFarland, PhD, International Electronic Journal of Health Education, 2009, 12:99-107

'Writing smaller', Clarity Journal no. 63, 2010

Plain Language Commission style guide, 2012

'Shorter Lines Facilitate Reading in Those Who Struggle', M. H. Schneps, J. M. Thomson, G. Sonnert, M. Pomplun, C. Chen, A. Heffner-Wong, 2013

'Towards a better measure of readability: Explanation of empirical performance results', L. A. Olsen, R. Johnson, Taylor and Francis Group, 2015

'What is plain language?', Plain Language Association International, 2015

Text complexity, ATOS, and Lexile® Measures, Renaissance Learning, 2016

'Understanding Plain English summaries. A comparison of two approaches to improve the quality of Plain English summaries in research reports.' E. Kirkpatrick, W. Gaisford, E. Williams, E. Brindley, D. Tembo, D. Wright, 2017

'How to use Yoast SEO: The readability analysis?' E. Toonen, Yoast, 2018

The Crystal Mark standard Plain English Campaign. Undated.

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